10,614 research outputs found
Space station integrated wall design and penetration damage control. Task 3: Theoretical analysis of penetration mechanics
The efforts to provide a penetration code called PEN4 version 10 is documented for calculation of projectile and target states for the impact of 2024-T3 aluminum, R sub B 90 1018 steel projectiles and icy meteoroids onto 2024-T3 aluminum plates at impact velocities from 0 to 16 km/s. PEN4 determines whether a plate is perforated by calculating the state of fragmentation of projectile and first plate. Depth of penetration into the second to n sup th plate by fragments resulting from first plate perforation is determined by multiple cratering. The results from applications are given
Signatures of Alfven waves in the polar coronal holes as seen by EIS/Hinode
Context. We diagnose the properties of the plume and interplume regions in a
polar coronal hole and the role of waves in the acceleration of the solar wind.
Aims. We attempt to detect whether Alfven waves are present in the polar
coronal holes through variations in EUV line widths. Methods. Using spectral
observations performed over a polar coronal hole region with the EIS
spectrometer on Hinode, we study the variation in the line width and electron
density as a function of height. We use the density sensitive line pairs of Fe
xii 186.88 A & 195.119 A and Fe xiii 203.82 A & 202.04 A . Results. For the
polar region, the line width data show that the nonthermal line-of-sight
velocity increases from 26 km/s at 1000 above the limb to 42 km/s some 15000
(i.e. 110,000 km) above the limb. The electron density shows a decrease from
3:3 10^9 cm^-3 to 1:9 10^8 cm^-3 over the same distance. Conclusions. These
results imply that the nonthermal velocity is inversely proportional to the
quadratic root of the electron density, in excellent agreement with what is
predicted for undamped radially propagating linear Alfven waves. Our data
provide signatures of Alfven waves in the polar coronal hole regions, which
could be important for the acceleration of the solar wind.Comment: 5 pages, 11 figures. Astronomy and Astrophysics Letters (accepted)
http://www.aanda.org/articles/aa/pdf/forth/aa12242-09.pd
From spin-Peierls to superconductivity: (TMTTF)_2PF_6 under high pressure
The nature of the attractive electron-electron interaction, leading to the
formation of Cooper-pairs in unconventional superconductors has still to be
fully understood and is subject to intensive research. Here we show that the
sequence spin-Peierls, antiferromagnetism, superconductivity observed in
(TMTTF)_2PF_6 under pressure makes the (TM)_2X phase diagram universal. We
argue that the suppression of the spin-Peierls transition under pressure, the
close vicinity of antiferromagnetic and superconducting phases at high pressure
as well as the existence of critical antiferromagnetic fluctuations above T_c
strongly support the intriguing possibility that the interchain exchange of
antiferromagnetic fluctuations provides the pairing mechanism required for
bound charge carriers.Comment: 4 pages, revtex, 4 figures (jpeg,eps,png
Strain enhancement of superconductivity in CePd2Si2 under pressure
We report resistivity and calorimetric measurements on two single crystals of
CePd2Si2 pressurized up to 7.4 GPa. A weak uniaxial stress induced in the
pressure cell demonstrates the sensitivity of the physics to anisotropy. Stress
applied along the c-axis extends the whole phase diagram to higher pressures
and enhances the superconducting phase emerging around the magnetic
instability, with a 40% increase of the maximum superconducting temperature,
Tc, and a doubled pressure range. Calorimetric measurements demonstrate the
bulk nature of the superconductivity.Comment: 4 pages, 4 figure
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